Is hyaluronic acid a moisturizer? Will it help dry skin?

What is a moisturizer? When applied to your skin, a moisturizer will prevent excess water loss preventing dry skin (xerosis). If you want to treat effectively a skin problem, you need to forget about “stories” and look at the molecular biology of the skin. Nothing more, nothing less. Applying topically what your skin makes internally will not necessarily help. Why not? Because it will not be in the right place at the right time.

What is dry skin? When human skin is subjected to conditions that it was not made to withstand: air conditioning, long bubble baths, repeat exfoliation, etc., you get dry skin: xerosis, dry skin in Greek (ksero, dry).  Don’t be confused by Latin or Greek; giving a problem a name doesn’t elucidate its cause.  It makes it sound more like a serious illness, but dry skin is a common problem with easy solutions.

Hyaluronic acid and ceramides have acquired an almost magical meaning because of the long-term advertising done by skincare companies. To appreciate their real value in skincare, you need to think outside the (advertising) box or let Skin Actives do the thinking and formulating.

Ceramides are part of the “cement” that binds corneocytes and help make your skin a barrier. There is no way that ceramides, applied topically, will help in the same way. They are not at the right place at the right time: to stick dead cells to each other when turning into corneocytes. Hyaluronic acid is inside your dermis; your skin makes it. Let’s look at what hyaluronic acid does inside the skin.

Hyaluronic acid (a.k.a. hyaluronan, sodium hyaluronate) is a polysaccharide made by animals and some bacteria, with long chains made of N-acetyl-D-glucosamine alternating with glucuronic acid. In our skin, it stabilizes the intercellular (in-between cells) space in the dermis and contributes significantly to cell proliferation, migration, and skin repair, activities essential to skin health. By definition, the molecular weight of hyaluronic acid is in the millions.  This huge molecule holds a  lot of water and helps give volume to the dermis; it also participates in healing, cell migration, inflammation, keratinocyte proliferation, and more.




Figure. Structure of hyaluronic acid. The “n” indicates that the subunit (glucuronic acid at left, glucosamine at right) between brackets is repeated thousands of times to form the very large polymer.

What about hyaluronic acid topically?

This large molecule absorbs water and forms a nice gel. It will dry on the skin as a film and stretch it as it dries. Hyaluronic acid in a cream may help keep water loss down, but it needs some other components like glycerol and silicones to do this particular job.

If you want more hyaluronic acid in your skin

Topical hyaluronic acid may help (a bit) by donating some N-acetyl glucosamine and glucuronic acid, if degraded by the enzyme hyaluronidase. But to make hyaluronic acid, go for epidermal growth factor and vitamin A (retinoids, beta carotene).

Why does dry skin happen?

The skin has a tough job. Our bodies are mostly water, and the skin separates the body from an environment that can be as dry as the weather in Arizona, today relative humidity is just 7%, a small fraction of the amount of water required to saturate the air with humidity at today’s temperature. Of course, the body will lose water through the skin! TEWL (trans-epidermal water loss) can be measured with specialized equipment.

What happens at the molecular level? The skin contains chemicals, produced during skin maturation from live cells to skin barrier that help retain moisture. But there can be a deficiency in moisture-binding substances collectively known as the natural moisturizing factor (NMF). NMF components are found in the stratum corneum and are located in high concentrations within the corneocytes. The NMF consists primarily of amino acids (~40%) and their derivatives, including pyrrolidone carboxylic acid (PCA, ~12%), lactate (~12%), urea (~7%), and inorganic salts (~18%). These hygroscopic chemicals attract and bind atmospheric water and internal water supplied from the dermis, allowing the corneocyte to remain hydrated despite the drying effects of the environment. The source of much of the NMF is filaggrin, a histidine-rich keratin binding protein. The skin uses whatever chemicals are around to solve a problem.

The same happens with ceramides. These chemicals play an important role in maintaining skin barrier function. Most skin disorders exhibiting dry skin conditions, such as atopic dermatitis, have been shown to have reduced or altered ceramide profiles in the stratum corneum resulting in decreased barrier function. Again, the skin uses whatever chemicals are around to solve a problem: “cementing” dead skin cells to make the skin barrier.

How do we solve dry skin?

We don’t have limitations: we have many chemicals to choose from. Let’s use ceramides and hytaluronic acid if we have to, but there are much better stuff to choose from. Skin Actives is now in the process of formulating a Moisturizing Factor to emulate (improve on) the one that our skin makes. We can do better than hayluronic acid and ceramides!

Hannah

References

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Pienimäki JP, Rilla K, Fülöp C, et al. Epidermal growth factor activates hyaluronan synthase 2 in epidermal keratinocytes and  increases pericellular and intracellular hyaluronan. J Biol Chem.  2001;276(23):20428‐20435.

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Weber, T. M., Kausch, M., Rippke, F., Schoelermann, A. M., & Filbry, A. W. (2012). Treatment of xerosis with a topical formulation containing glyceryl glucoside, natural moisturizing factors, and ceramide. The Journal of clinical and aesthetic dermatology, 5(8), 29–39.